Portable mattress



FIG. 1 is a side elevational view of a portable mattress showing my new design, the opposite side being a mirror image of that shown;

FIG. 2 is an end elevational view thereof, the opposite end being a mirror image of that shown;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a perspective view thereof;

FIG. 6 is a perspective view thereof, showing the mattress in a partially folded condition;

FIG. 7 is a side elevational view thereof, showing the mattress in a completely folded position;

FIG. 8 is a perspective view thereof, showing the mattress in a completely folded and partially zippered closed condition; and

FIG. 9 is a perspective view thereof, showing the mattress in a folded and zippered closed condition. 

The ornamental design for a portable mattress, as shown and described. 